Running wire from solar panels to equipment 100 feet away

circus

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I've already arranged to send back the controller.
AMPINVT 60 amp 12V/24V/36V/48v DC 150V PV Input MPPT Solar Charge Controller
Excuse me, are you sending this charge controller back? Why?
It's not familiar but sounds good.
 

wattmatters

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I have a similar length cable run.

My AIO inverter has rather low Voc max of 105V.

I wired 6x370W Longi panels in a 2S3P configuration into a combiner box located under the panels (inside the garage upon which the panels are). Then ran a 6mm² (~10AWG) copper solar cable the 30 metres (~100 feet) from the output of the combiner box to the AIO unit.

Works perfectly fine.

Sure there are probably some energy losses running at lower voltage but so what? Having an inverter with a much higher Voc limit would have been good, but don't let perfect be the enemy of good. I don't have room for more panels on that roof anyway, so spending more (at least double) for a higher spec'd inverter just wasn't worth it.

If I wanted/needed to have a much larger solar PV array (either now or eventually) then I would have chosen a different inverter with MPPT inputs with much higher Voc.
 

wiseacre

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Curious to know the details! Hoping it adds to this thread, not trying to hijack...
Not to worry, I'd welcome those details. Seeing what others do is informative

There are Growatts that will take much higher voltages such as the SPF5000US which will take up to 450V DC. Some versions they have even have multiple independent MPPT inputs so you could have 2 separate arrays go into same all in one. I believe the ones with the lower voltage limit like you mentioned are the older ones. One thing to take note about some of these cheaper all-in-ones is they tend to be noisy because of a fan running constantly to cool them off. I almost considered an MPP solar LV model until I found out the fan was really noisy and ran constantly :)
noise is not a problem, the constant power consumption of the fans might add up to more than I want to sacrifice
up to 450 😀

I haven't seen a SPF5000US do you have a link?

 

wiseacre

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Excuse me, are you sending this charge controller back? Why?
It's not familiar but sounds good.
I've changed my plans.
I was going to use it for my current system and begin building a new system but I decided to upgrade it instead with future expansion in mind. I'm looking at much higher input voltages now.
 

wiseacre

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I have a similar length cable run.

My AIO inverter has rather low Voc max of 105V.

I wired 6x370W Longi panels in a 2S3P configuration into a combiner box located under the panels (inside the garage upon which the panels are). Then ran a 6mm² (~10AWG) copper solar cable the 30 metres (~100 feet) from the output of the combiner box to the AIO unit.

Works perfectly fine.

Sure there are probably some energy losses running at lower voltage but so what? Having an inverter with a much higher Voc limit would have been good, but don't let perfect be the enemy of good. I don't have room for more panels on that roof anyway, so spending more (at least double) for a higher spec'd inverter just wasn't worth it.

If I wanted/needed to have a much larger solar PV array (either now or eventually) then I would have chosen a different inverter with MPPT inputs with much higher Voc.
I have room for more panels at greater distances so the idea of greater Voc is now my first priority. I see panels with twice the output and the same price I paid for mine so I agree a bit of loss wouldn't hurt either
 

wattmatters

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I have room for more panels at greater distances so the idea of greater Voc is now my first priority. I see panels with twice the output and the same price I paid for mine so I agree a bit of loss wouldn't hurt either
That makes sense. Taking some time to scope out the project is worthwhile. Scope creep is a challenge though.

With panel choice I was original going to use 10x250W panels in 2S5P but those panels became a bit harder to get for various reasons, meanwhile the second hand 370W panels turned out to be easy to get and cheap. The installation and cabling for 6 panels was way easier than trying to do 10 panels.

Having now done it, I doubt I've have been able to put 10 panels up anyway. It was going to require more infrastructure than the garage was really set up for, meanwhile the 6 x 370W panels were able to be fitted with rails secured to using existing roof battens. Trying to fi a 10 panel arrangement was going to need extra roofing battens.

It also mean much less cable was required for the 30m run. For a 3P arrangement 1 x 6mm cable was all that was required, else with a 5P set up I was either going to need 2 runs of that cable for double the cost or a thicker gauge cable which was going to be more than double the cost.

Just for fun I went out this morning (~9:30am) to measure voltages at the combiner box to compare with the inverter reading. IOW either end of the 30m cable run.

I did this before and after the pool pump started up to see the difference between a very lightly loaded case (just float current into batteries and inverter's own power draw) and a loaded case (pool pump drawing ~950W on its 5-min start up cycle).

With a light load (~250-300W) the voltage drop was ~1V or so
With the load at a bit under 1kW the voltage drop was ~3.5V

I just compared that with this voltage drop calculator:

The voltage drops I measured are right in line with the calculator.
 

wiseacre

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I'm not sure what numbers to plug in. The only amp/voltage listed on my panels is
195w -12v panel
  • Open-Circuit Voltage (Voc): 22.8V
  • Short circuit current (Isc): 12.23A
  • Working current (Iop): 10.27A
That Volt spec I know not to use use and there is no other listing. It's called a 12 v panel but I assume it's operating v is higher. Given a choice I plugged 12x6 = 72w and 10a into the calculator and got 6 mm2 and a run of 28.1 m. (10 AWG and 92 feet)

very good looking numbers, and I assume the 12v is on the low side of what it is actually (since the panel voltage has to be higher than my 24v battery to charge), too good to be true?
A single 100 ft with 10AWG solar cables
and close to 150 ft with 8awg cables
 

wattmatters

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I'm not sure what numbers to plug in.
The operating voltage will be lower than the Voc. Somewhere around 19V and it will vary depending on the charge controller / MPPT so it's only indicative.

The voltage of the string will depend on how many panels you plan to put in series. e.g. 2S = 38V, 6S = 114V.
 

wiseacre

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The operating voltage will be lower than the Voc. Somewhere around 19V and it will vary depending on the charge controller / MPPT so it's only indicative.

The voltage of the string will depend on how many panels you plan to put in series. e.g. 2S = 38V, 6S = 114V.
Thanks, that helps. I'm slowly getting an understanding
 

iamrich

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I'm not sure what numbers to plug in. The only amp/voltage listed on my panels is
195w -12v panel
  • Open-Circuit Voltage (Voc): 22.8V
  • Short circuit current (Isc): 12.23A
  • Working current (Iop): 10.27A

You want to use the VOC and ISC to determine your controller size. And really you should leave some room on the voltage side (20%) just in case it gets cold.

You can figure the voltage of the panel by taking the wattage rating and dividing by the working current.

195w/10.27a=18.98v, so you definitely need to series these panels (at least two, three would be better) to get the voltage over 24v.
 

wiseacre

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I am not sure I would even use a combiner box in this case. I would just combine with a branch connector and use 10awg in conduit, or run 2 sets of 12awg in a conduit from the panels to the controller and use a MC4 branch connector at the controller. Put a couple of 15amp fuses inline. You are pushing ~66v at ~22a max so 10awg should do it. You are a little close to max voltage, so use the 100-150ft voltage drop to your advantage.
I keep reviewing this thread (among others) and your suggestion is now making some sense to me.

Using inline fuses, you said 10 amp fuses, I take it that it would be on any series combination (2 to 4s) before using a branch connector.
(volts add up, amps remain the same in series).

I now have 8 of the 195w panels and distance to the SCC is now cut by more than half (under 50 ft, wife's herb garden is doomed)
thinking of doing 4s2p ~~ 132v, 22a - then it becomes 132v, 44a?
actually someone said my voltage per panel is closer to 19V, so if I rounded that up to 25v adjusting for cold temp operation I get 100v with 4 in series )

In that case I'd need a 150v, 60amp CC
if I wanted to expand the array (example 4s3p) could I use a second branch connector to make 132v, 66a?

part of all this is to select the right sized CC (looking at 150v, 80a)
Two CCs are on my list
  • 80a. 250v -Growatt CC only
  • 80a. 150v Outback Flexmax
I like the Growatt but haven't seen any reviews so have doubts. The price is more attractive

I have a ton more questions but I'll stop here and try to digest this first. I'm not sure I got the first bite chewed properly.
 
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wiseacre

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If your Voc is 132V then 150V SCC would be ok unless it gets REALLY cold where you are.

195W x 6 = 1170W
1170W / 25.6V battery = 45.7A charging current max from your array.
I've seen it go to -40F
195w/10.27a=18.98v, so you definitely need to series these panels
so to keep it simple with plenty of fudge factor for me could I use 25v as a single panel's Voltage?
then 4s = 100v which should be plenty to safety factor in the extreme cold.
 

MisterSandals

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I've seen it go to -40F

so to keep it simple with plenty of fudge factor for me could I use 25v as a single panel's Voltage?
then 4s = 100v which should be plenty to safety factor in the extreme cold.
The panels are rated at 25 deg C. The voltage increase (use Voc for this) is .3% ** for every degree the temp drops below 25 deg C. Your panel voltage is 21.6V.

-40F is a convenient temp, its also -40C
Thats a drop of 65 deg C.
Some math:

65 x .003 x 21.6V = 25.8V

** use the appropriate thermal coefficient for YOUR panels. They are generally .3-.4%.
 

TRW

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I am sorry, if this was answered, I was not at the end of the thread when I posted.
 

Guido1

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Thanks, that helps. I'm slowly getting an understanding
Hello

I'm dealing with similar issues on the off-grid system I'm installing.
The shortest distance from the clearing where I might be able to mount PV's to an enclosure (small barn) is 150'.
I'm not eager to have both my (8) SOK 206 amp batteries and my 48 volt 12k Sigeneer AIO inverter/charger outside just to gain proximity to the panels, the installation will be about 150 yards from my house, and there are a lot of trees obscuring visibility. The barn is still 100 yards or so from my house, but that will be an AC run.
I was originally going to run my batteries in 2S4P to obtain the 48v required, now I'm facing how to safely and economically run my DC wiring from PV's to AIO and batteries.
Now, I'm wondering what would be the optimal configuration for the DC wiring? I'm likely to add panels as I can obtain them.

Here's the Sigeneer spec's:

PECIFICATIONS​

Inverter Output Specifications:
•Continuous Output Power: 12000 Watts
•Surge Rating: 36000 Watts (5 Seconds)
•Output Voltage: 104/208V, 110/220V, 115/230V, 120/240Vac (resetable on LCD)
•Nominal Efficiency: 91% (Peak)
•Line Mode Efficiency: >95%
•Output Frequency: 50Hz +/- 0.3Hz / 60Hz +/- 0.3Hz
•Typical Transfer Time: 10ms (Max)
•THD: <10%


DC Input Specifications:
• Nominal Input Voltage: 48.0Vdc
• Low Battery Cutoff: 40.0-48Vdc
• Low Battery Alarm: 42-50Vdc
•DC to AC Transfer in SBU or Solar first mode: 44-51.2V
•AC to DC Transfer in SBU or Solar first mode: 48-58V
• High Voltage Cutoff: AGM:60V/FLD:62V/ USE mode: C.V+4V
• High Voltage Recovery: 58V
——————
DC Input Specifications(Lithium version):
• Low Battery Cutoff: 5%-30% SOC
• Low Battery Alarm: Low Battery Cutoff SOC+5%
•DC to AC Transfer in SBU or Solar first mode: 20%-50% SOC
•AC to DC Transfer in SBU or Solar first mode: 60%-100% SOC
• High Voltage Cutoff: AGM:60V/FLD:62V/ USE mode: C.V+4V
• High Voltage Recovery: 58V
————
• Idle Consumption: 180 Watts
• Power Saver Mode Idle Consumption:40 Watts


Charger Specifications:
• Ac Input Voltage For Charger: Nominal 240Vac (154-260Vac)
• Output DC voltage: 48-58.4V Depends on battery Type
• AC Charger Rate: 100Amp
• Solar Charger Rate: 120Amp
• Max Combined Charge Rate: 180Amp
• Over Charge Protection Shutdown: 62.4V
• Adjustable charge current: 0-100%
• Four Stage Smart Charger

I can get panel spec's, just don't have them at my fingertips.
Any ideas on DC wiring?
 

rhino

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@Guido1 You need to provide the max Voc that the inverter/charge controller you plan to use can take. Just in general, the higher the voltage the smaller the gauge of wire you can use. I have mine about 600ft away and am "only" using charge controller that can take up to 250V Voc. It somewhat depends on what your preferences and priorities are.
 

iamrich

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Hello

I'm dealing with similar issues on the off-grid system I'm installing.
The shortest distance from the clearing where I might be able to mount PV's to an enclosure (small barn) is 150'.
I'm not eager to have both my (8) SOK 206 amp batteries and my 48 volt 12k Sigeneer AIO inverter/charger outside just to gain proximity to the panels, the installation will be about 150 yards from my house, and there are a lot of trees obscuring visibility. The barn is still 100 yards or so from my house, but that will be an AC run.
I was originally going to run my batteries in 2S4P to obtain the 48v required, now I'm facing how to safely and economically run my DC wiring from PV's to AIO and batteries.
Now, I'm wondering what would be the optimal configuration for the DC wiring? I'm likely to add panels as I can obtain them.

Here's the Sigeneer spec's:

I can get panel spec's, just don't have them at my fingertips.
Any ideas on DC wiring?
Manual says 8awg is as big as you can go, with 150v/250v.

1631734472178.png
 
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